TWO local government areas (LGAs) on the Northern Rivers take some of the top spots for the most cannabis offences in the State, a crime which costs the NSW economy $700 million a year, a new report states.

The NSW Auditor-General yesterday released his findings on the effectiveness of police issuing cautions to people in possession of minor amounts of cannabis (less than 15 grams).

Eight per cent of the NSW population are cannabis users, the report found, a large proportion of which are on the Northern Rivers.

The Byron Shire and Lismore LGAs took the second and third spots for the highest number of cannabis possession offences in the State, exceeded only by Sydney.

While cannabis cautioning has saved at least $20 million in court costs over the past 10 years, very few adults and even fewer youths sought help for their drug use, Auditor-General Peter Achterstraat said.

“Police do not have the authority to compel young offenders to seek help for their cannabis use.

The police can only issue a caution and refer them to a local drug treatment services,” he said in a statement.

Fewer than two-in-five adults cautioned for a second time used a drug helpline, despite it being mandatory.

Mr Achterstraat recommended the NSW Police and NSW Health work towards increasing the number of adult offenders contacting the NSW drug helpline.

Twenty-five per cent of patients who seek help from the Northern NSW Local Area Health Network drug and alcohol service do so for cannabis use, the service's director John Leary said.

“It's a good recommendation that they should attempt to increase the number of people seeking treatment,” he said.

“We could provide more information and education to the police to both inform and to get out to thepeople they see that our local service is available.”

HEMP Embassy president Michael Balderstone said the $700 million figure placed on taxpayers would be a lot higher if cautioning was abolished.